Neuroprotective Effects of Aldehyde-Reducing Composition in an LPS-Induced Neuroinflammation Model of Parkinson's Disease

Abstract

Parkinson's disease (PD) is a complex neurodegenerative disease in which neuroinflammation and oxidative stress interact to contribute to pathogenesis. This study investigates the in vivo neuroprotective effects of a patented yeast extract lysate in a lipopolysaccharide (LPS)-induced neuroinflammation model. The yeast extract lysate, named aldehyde-reducing composition (ARC), exhibited potent antioxidant and anti-aldehyde activities in vitro. Oral administration of ARC at 10 or 20 units/kg/day for 3 days prior to intraperitoneal injection of LPS (10 mg/kg) effectively preserved dopaminergic neurons in the substantia nigra (SN) and striatum by preventing LPS-induced cell death. ARC also normalized the activation of microglia and astrocytes in the SN, providing further evidence for its neuroprotective properties. In the liver, ARC downregulated the LPS-induced increase in inflammatory cytokines and reversed the LPS-induced decrease in antioxidant-related genes. These findings indicate that ARC exerts potent antioxidant, anti-aldehyde, and anti-inflammatory effects in vivo, suggesting its potential as a disease-modifying agent for the prevention and treatment of neuroinflammation-related diseases, including Parkinson's disease.

Keywords: ALDH; Parkinson’s disease; neuroinflammation; oxidative stress.

Figure 1

Antioxidant and anti-aldehyde effects of ARC. (a) Antioxidant effects. DPPH inhibition (%) of yeast extract ARC, inactive dry brewer’s yeast (DBY), quercetin (QU), and ascorbic acid (AA). (b) Anti-aldehyde effects. The concentration of 3,5-DHBA-acetaldehyde derivatives was determined in the presence of ARC, DBY, QU, or AA. Data are the mean ± SEM (n = 5). * p < 0.05, ** p < 0.01, *** p < 0.001 vs. CTL.

Figure 2

Protective effects of ARC on nigrostriatal dopaminergic neurons in LPS-injected mice. C57/BL6 mice (8 weeks, 19–23 g) were intraperitoneally injected with PBS (CTL), or LPS (10 mg/kg in PBS). ARC (0, 10, 20 units/kg/day) or QU (10 mg/kg/day, reference) was orally administered once a day for 3 days before the injection of LPS (10 mg/kg, i.p.) or PBS. At 3 h after LPS injection, mice were sacrificed and transcardially fixed. The brain sections were then prepared for immunohistochemical staining. (a) Experimental scheme. (b) Dopaminergic neurons were visualized by immunohistochemical staining with an anti-TH antibody in the ST and SN. (c) The number of TH-positive neurons and (d) optical density of TH-positive fibers in the ST was measured. Data represent the mean ± SEM (n = 5). * p < 0.05, ** p < 0.01, *** p < 0.001 vs. CTL, # p < 0.05, ## p < 0.01, ### p < 0.001 vs. LPS-injected vehicle.

Figure 3

ARC suppresses LPS-induced activation of astrocytes and microglia in the SN. Mice brain sections were prepared as described in Figure 1. (a,c) Representative images of coronal brain sections containing the SN immunostained with anti-Iba-1 ((a), microglia) or anti-GFAP ((c), astrocytes) antibodies. Boxes in SN regions were enlarged to visualize activated microglia or astrocytes. (b,d) Quantitative analysis of microglia (b) or astrocytes (d). Upper graph, quantification of the number of activated microglia or astrocytes per section. Lower graph, comparison of the number of activated microglia or astrocytes (Activated) versus total Iba-1- or GFAP-positive cells (Total). Data represent the mean ± SEM (n = 5). * p < 0.05, *** p < 0.001 vs. CTL, ## p < 0.01, ### p < 0.001 vs. LPS-injected vehicle.

Figure 3

ARC suppresses LPS-induced activation of astrocytes and microglia in the SN. Mice brain sections were prepared as described in Figure 1. (a,c) Representative images of coronal brain sections containing the SN immunostained with anti-Iba-1 ((a), microglia) or anti-GFAP ((c), astrocytes) antibodies. Boxes in SN regions were enlarged to visualize activated microglia or astrocytes. (b,d) Quantitative analysis of microglia (b) or astrocytes (d). Upper graph, quantification of the number of activated microglia or astrocytes per section. Lower graph, comparison of the number of activated microglia or astrocytes (Activated) versus total Iba-1- or GFAP-positive cells (Total). Data represent the mean ± SEM (n = 5). * p < 0.05, *** p < 0.001 vs. CTL, ## p < 0.01, ### p < 0.001 vs. LPS-injected vehicle.

Figure 4

ARC suppresses pro-inflammatory cytokine mRNA expression in the liver of LPS-injected mice. Hepatic total RNAs of LPS-injected mice were isolated using Trizol reagent. Pro-inflammatory cytokine mRNA was quantified using real-time RT-qPCR. (a) IL-1β, (b) IL-6, and (c) TNF-α mRNA expression were graphed. Data represent the mean ± SEM (n = 5). *** p < 0.001 vs. CTL, ## p < 0.01, ### p < 0.001 vs. LPS-injected vehicle.

Figure 5

ARC increases the mRNA levels of antioxidant genes in the liver of LPS-injected mice. Hepatic total RNAs of LPS-injected mice were isolated using Trizol reagent. The mRNA levels of antioxidant genes were determined by real-time RT-qPCR. Relative mRNA levels of (a) NQO1, (b) SOD, (c) HO-1, (d) Sirt1, (e) Sirt2, and (f) Sirt3 were graphed. Data represent the mean ± SEM (n = 5). * p < 0.05, ** p < 0.01, *** p < 0.001 vs. CTL, # p < 0.05, ## p < 0.01, ### p < 0.001 vs. LPS-injected vehicle.